The present invention relates to semiconductor structures, and particularly to semiconductor structures having lattice mismatched semiconductor layers on the same lithographic level and methods of manufacturing the same.
Group IV element based semiconductor devices, e.g., silicon and/or germanium based semiconductor devices, are commonly used in the semiconductor industry to form semiconductor chips in part due to availability of group IV element semiconductor substrates. Particularly, silicon based substrates containing silicon, silicon germanium alloy, or silicon carbon alloy are commonly available in semiconductor industry at a low cost. In the case of silicon substrates, wafers having a diameter of 300 mm are commonly used in mass manufacturing. Thus, group IV element based semiconductor devices, and particularly, silicon based devices, formed on silicon containing substrates form a majority of semiconductor components utilized in semiconductor chips.
A compound semiconductor is a semiconductor comprising elements from two or more different groups of the periodic table. Compound semiconductors may be binary, ternary, or quaternary, i.e., may have two, three, or four distinct elements. Exemplary III-V binary compound semiconductors include AlN, AlP, AlAs, GaN, GaP, GaAs, InP, InAs, InSb, etc. Exemplary II-VI compounds include ZnS, ZnSe, ZnTe, CdTe, HgTe, etc. Exemplary ternary compound semiconductors include AlInGaP, AlGaAs, InGaN, and CdHgTe. Exemplary quaternary compound semiconductors include InGaAsP.
Semiconductor devices formed from compound semiconductors may offer performance advantages over silicon based semiconductor devices. For example, GaAs has a higher saturated electron velocity and higher electron mobility than silicon, enabling a higher device operation frequency. Also, GaAs devices in general have higher breakdown voltages and generate less noise during a high frequency operation than silicon based devices of comparable dimensions. Further, the band structure of GaAs contains a direct band gap between the conduction band and the valence band, enabling emission of light. For the above reasons, GaAs circuitry is employed in communication devices, microwave devices, and radar systems. Likewise, other compound semiconductors offer distinct advantages over silicon for some semiconductor applications.
In general, compound semiconductors and/or semiconductor devices formed therefrom also have some disadvantages compared with group IV semiconductor elements. For example, mechanical strength of compound semiconductors tends to be inferior to that of group IV semiconductor elements, especially that of silicon. Also, compound semiconductor substrates are harder to manufacture than group IV semiconductor element substrates, especially silicon substrates. This is because silicon is highly abundant on earth as silicates, while the compound semiconductor material tends to be rarer than silicates. Further, stable oxides of compound semiconductors are rare while silicon dioxide may be readily formed and serves as a stable dielectric material.
Therefore, integration of a compound semiconductor material in a group IV semi-conductor element substrate to form group IV element based semiconductor devices and compound semiconductor devices to utilize their respective advantages is desired. However, integration of a single crystalline compound semiconductor material with a single crystalline group IV semiconductor element has proved to be challenging since compound semiconductors are in general formed by processing methods that are uncommon with standard semiconductor processing technologies. Further, due to lattice mismatch between group IV semiconductor elements and compound semiconductors, formation of a single crystalline compound semiconductor layer on a single crystalline group IV semiconductor element containing substrate typically involves bonding of two semiconductor materials.
Prior art methods of integrating a compound semiconductor material into a group IV semiconductor element substrate by growing a thick buffer layer on a group IV semiconductor element substrate, followed by deposition of a compound semiconductor layer, have the disadvantage of requiring a thick epitaxial growth of buffer layers. Further, only the compound semiconductor layer is exposed on the top of the substrate after deposition of the compound semiconductor layer, thus making the portion of the group IV semiconductor element underneath the compound semiconductor layer inaccessible for further processing. This approach is also very inconvenient for semiconductor devices employing both a compound semiconductor material and a group IV semiconductor material simultaneously.
In view of the above, there is a need to provide a semiconductor structure having a group IV semiconductor material and a compound semiconductor material in proximity of each other on the same lithographic level.
In addition, there exists a need for a semiconductor structure having lattice mismatched semiconductor layers, e.g., a group IV semiconductor element layer and a compound semiconductor layer, on the same lithographic level and methods of manufacturing the same.
Further, there exists a need for a semiconductor structure formed on a silicon substrate and having an exposed group IV semiconductor element layer for forming group IV semiconductor element based devices and an exposed compound semiconductor layer for forming compound semiconductor devices at the same lithographic level and methods of manufacturing the same in an economical manner.